Good for you flipper! To those who say, why bother, she's in her eighties? I think Flipper made a good point, that although he most likely isn't going to convert her, her opening her mind to think for herself can have a trickling effect on younger family members. My aunt cared for my grandmother, her mother, until her death, bathed her, changed her, she was a great daughter, the last word's from my grandmother's lips to her, on her deathbed were that she could never forgive her for leaving Jehovah. If Flipper or anyone can be spared that kind of harshness and cruelty by at least getting their elderly family members to understand why they feel the way they do and respect the choices they make, to some degree, I say go for it.
Those words still haunt my Aunt to this day. A little understanding can go a long way, if Flipper can achieve that with his mother, more power to him.